Method and device for assessing the surface condition of a material

ABSTRACT

A device for evaluating the surface condition of a material and a method derived from it, based on the use of an element which vibrates under the influence of relative movement with respect to the surface to be assessed. This method allows the analysis of any surface, with or without surface periodicity, regardless of its constitution or its composition, and regardless of any surface treatment(s) it may have undergone. The evaluation device ( 1 ) comprises a support ( 2 ) to which is attached at least one vibrating element ( 3 ) capable of vibrating upon contact with the surface of the material surface ( 5 ), the vibrating element ( 3 ) being driven to move relative to the material surface ( 5 ). The evaluation device ( 1 ) also comprises a mechanism ( 4 ) for measuring the particular vibrating modes by the vibrating element ( 3 ) which furnishes a signal corresponding to a particular vibration modes, a device ( 6 ) for processing and analyzing the signal which produces one or more elements of data characterizing a surface condition, and an interface ( 7 ) which display the one or more elements of data.

FIELD OF THE INVENTION

The present invention concerns a device for assessing the surfacecondition of a material and a method using said assessment device,especially for characterizing the softness to touch of a material.

BACKGROUND OF THE INVENTION

It is important in several domains to determine the surface condition ofa material or changes in the surface condition. The condition dependsupon the material under consideration: fibrous material; textile; humanor animal skin; human or animal hair or fur; paper for writing,printing, cleaning, hygiene, or packaging; metal, animal, mineral orvegetable material; wood; or plastic materials. For example, in textilemanufacturing, fabric treatment might cause the appearance ofmicrofibers, which increases fabric softness. In certain cases it isuseful to quantify the modifications to the surface of a material inorder to determine a measurement of softness to the touch. By way ofexample, this measurement of softness to touch may be used bymanufacturers of laundry products, detergents, and household products totest the quality of their products just as it is done in the cosmeticsindustry.

At the present time a first type of apparatus for measuring thetopography of the surface to be analyzed exists, for example, anapparatus using an optical, mechanical, or imaging method. The surfaceprofile is then studied using several techniques:

Statistical methods: in this case, the profile is considered as apopulation of elements defined by two or three coordinates. Analysisconcerns first, the height of the asperities (average, deviation fromaverage, disparity-type, obliqueness, fineness, etc.) and then theirdistribution over the surface (average distance between two asperities,etc.)

The usual methods: used in signal processing, such as frequencyanalysis, temporal analysis, time-frequency analysis, etc.

Chaotic methods: such as fractal analysis.

A second type of apparatus exists which directly measures the behaviorof a surface when it is rubbed using a mechanical palpator. In thiscase, the measured signal is studied in a transitory or permanent regimewith the usual signal processing methods, the statistical or chaoticmethods cited above.

Each of these different investigatory methods has its disadvantages. Thestatistical methods used to measure topography or rubbing actually lackthe sensitivity required for certain applications because theinformation is gathered as a whole and important differences in thesurface state may be buried in the signal, resulting in an analysis thatlacks discrimination. Moreover, it is necessary to determine what is themost sensitive parameter of the surface for analysis, and it is ratherdifficult to extract a unique, universal parameter.

Insofar as the usual signal processing methods are concerned, they maybe very precise in the case of periodic surfaces but they do not adaptwell to non-periodic surfaces. Furthermore, they use comparative methodsand never absolutes.

Finally, chaotic methods, particularly calculation of fractaldimensions, have the same disadvantages as statistical analysis becausethey consider all the data resulting from the measurement.

Numerous applications using these methods are known. However, theseapplications are not based upon actual analysis of an element vibratingin contact with the surface.

This is the specific case with the device described in publicationnumber JP-A-10 269 868 for measuring the rugosity of an electrical cabledisplaced under a flexible plate. This device merely measures thedeflection of the flexible plate.

This is also the case with the device described in publication numberU.S. Pat. No. 5,672,929 for detection of vibrations generated bydisplacing a support such as a sheet of paper. The vibrations are thenanalyzed to determine contact and movement, but not the surfacecondition of the support.

SUMMARY OF THE INVENTION

The present invention proposes remedying these problems with anevaluation device and a method for analyzing a surface which may or maynot have surface periodicity, characterizing it using one parameter, andcomparing surfaces of completely different structures, textures,component materials, and possible surface treatments.

The present invention comprises a support to which at least onevibrating element is attached and is capable of vibrating upon contactwith the surface of the material, with the vibrating element movingrelative to the surface of the material. The evaluation device alsocomprises a means for measuring the particular vibration modes of thevibrating element in order to furnish a signal corresponding to saidparticular vibration modes, a device for processing and analyzing thesignal in order to extract at least one element of data about thesurface condition, as well as an interface to display the one or moreelements of data.

In a particularly advantageous manner, the evaluation device maycomprise a second processing device for transforming said datacharacterizing the surface condition into a value quantifying thematerial's softness to touch as a function of at least one predefinedcriterion.

The material may be selected from the group comprising metals, organic,mineral, natural or artificial material, synthetic material, or acomposition of several of these materials. In particular, it may be aliving material, such as skin or hair.

The vibrating element may be selected from the group comprising metals,organic, mineral, natural or artificial material, synthetic material, ora composition of several of these materials.

The means for measuring the particular vibration modes of the vibratingelement may consist of sensors which measure at least one physicaldimension associated with the vibrating element, such as kinematicdimensions (displacement, speed, acceleration) or dynamic dimensionsassociated with the vibrating element (force, moment) or with thematerial (constraint, deformation, deformation speed). The sensors mayalso measure at least one dimension associated with the correspondingenvironment (acoustical and thermal dimensions). The sensor or sensorsare founded on a technology selected from a group comprising at leastthe following technologies: mechanical, acoustical, electrical,electrostatical, electromagnetic, electronics, optical, optoelectronic,chemical, thermal, radioactive, or a combination of these technologies,using fluid as the media, the state of the fluid being chosen from thegroup comprising at least the viscous, liquid, or gaseous state.

Advantageously, the signal processing and analysis device producessignal analysis using a method selected from the group comprising atleast mathematics or physics.

The analysis method is preferably a physics method designed to effectsignal transformation selected from the group comprising at leastFourier transformation, time-frequency transformation, or wavetransformation. Any other mathematics or physics method of analyzing ananalog, discrete, quantified, or digital signal may also be used.

The vibrating element is attached to a support at an angle with amechanical connection selected from the group comprising one of thefollowing mechanical connections: unidirectional or bidirectional pivot,sliding pivot, spherical pivot with a finger, spherical pivot without afinger, linear, sliding, plane abutment, or point abutment, allowing itbetween 0 and 5 degrees of movement.

In a particularly advantageous method, the evaluation device of theinvention comprises a protective housing for the vibrating element andits support, said housing comprising at least one opening for a portionof the vibrating element to pass through. The means for measuring theparticular vibration modes, the processing and analysis device, and theinterface may be partially or completely contained within the housing.

The invention also concerns a method using the evaluation devicedescribed above in which said evaluation device is move relative to thematerial so as to cause the vibrating element to vibrate, the particularmodes of vibration by the vibrating element are measured using saidmeans for measuring particular modes of vibration, and the resultingsignal is processed and analyzed using the processing and analysisdevice in order to obtain at least the data corresponding to the surfacecondition of the material.

In a particularly advantageous embodiment, said data characterizing thesurface condition of the material may be transformed into at least onevalue quantifying the softness to touch of the material according to atleast one predefined criterion.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the present invention will be more readily apparentfrom the following description of several embodiments, with reference tothe attached drawings, in which:

FIGS. 1 through 3 are schematic illustrations of three embodiments andthe use of the evaluation device according to the invention;

FIGS. 4 and 5 represent the surface condition of a material before andafter treatment, respectively;

FIG. 6 represents the spectrums obtained after the method of theinvention is applied using the evaluation device of FIG. 2;

FIG. 7 shows a variation in the embodiment of the evaluation device ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, evaluation device 1 of the invention is usedto measure the surface condition of a textile material 5 that is movingrectilinearly in the direction of production shown by arrow A.Evaluation device 1 comprises a support 2 housing one extremity of avibrating element consisting of a rectangular blade 3 made of very thinsteel. Attached to said blade 3 there is an extensometric gauge 4 whichconstitutes the means for measuring the particular modes of vibration byblade 3 and which emits a signal corresponding to the particular modesof vibration by blade 3.

Evaluation device 1 is also equipped with a spectrum analyzer 6connected to gauge 4 and constitutes a device for processing andanalyzing the signal furnished by said gauge 4. Signal analysis isolatesthe frequencies and amplitudes of each particular vibration mode, eachvibration mode being capable of providing different data and evolvingdifferently according to how much energy is required by blade 3 tovibrate in the mode under consideration. The spectrum analyzer 6 isdesigned so that, via a Wheatstone type equilibrium bridge andprocessing the signal using Fourier transformation, for example, thespectral density of power as a function of the frequency of vibration byblade 3 is obtained. The spectrum obtained may be viewed directly on anInterface 7. The amplitude and energy of vibration shown on the spectrumprovide data characterizing the surface state of the textile material.Signal processing may also be accomplished using time-frequencytransformation and/or wave transformation.

Evaluation device 1 may also comprise a second processing device 6′transforming the data obtained from the angle of the spectrum into avalue determined relative to a predefined scale as a function of thevibrating element or the means of vibration measurement, and accordingto the condition of the entire surface analyzed. The value thus obtainedquantifies the softness to touch of the textile material 5 as a functionof certain predefined criteria.

Evaluation device 1 is used according to the following method to performon line measurements: support 2 is attached, for example, on anemerizer, above the textile material 5 moving in direction A. It isplaced at a distance from moving textile material 5 such that the freeend of blade 3 rubs against said textile material 5 and said blade 3bends slightly. Because of the textile-plate interaction, the platebegins to vibrate in its particular modes. Extensometric gauge 4 thenmeasures the relative deformations of blade 3 in the dynamic vibratingstate and transmits the corresponding signal to the spectrum analyzer 6.Processing the signal provides a visual representation of the particularvibration modes of blade 3 as peaks of spectral power density atfrequencies corresponding to these modes. The amplitude of these peaksis measured in V²/Hz and any variation in amplitude signifies amodification to the state of the surface being analyzed.

With reference to FIG. 2, evaluation device 10 according to theinvention is used to measure the surface condition of a sample oftextile material 15 attached to a revolving plate and moving in acircular direction according to arrow B for the purpose of performinglaboratory measurements. Evaluation device 10 comprises a support 12housing one extremity of a vibrating element consisting of rectangularblade 13 made of very thin polyvinyl chloride. In this variation, themeans for measuring the particular vibration modes is a microphone 14connected to an spectrum analyzer 16 which is itself connected to aninterface 17.

Spectrum analyzer 16 is selected for the same purpose as spectrumanalyzer 6, that is, to transform the signal emitted by microphone 14into spectral power density as a function of frequency, with the resultbeing displayed on interface 17.

Here again it is possible to provide in evaluation device 10 a secondprocessing device which transforms the data obtained from the angle ofthe spectrums into a value determined in relation to a predefined scaleas a function of the vibrating element or of the means for measuringparticular vibration modes, according to the condition of the entiresurface analyzed. The value obtained quantifies softness to touch of thesample of textile material 15 as a function of certain predefinedcriteria.

Evaluation device 10 is used according to the following procedure toperform laboratory measurements: support 12 is attached above textilematerial 15 moving in direction B. It is placed at a distance frommoving textile material 15 so that the free end of blade 13 rubs againsttextile material 15 and said blade 13 bends slightly. Because of thetextile-plate interaction, the plate begins to vibrate in particularmodes. Next, in a silent atmosphere, microphone 14 is placed somemillimeters away from the area where the plate rubs against the textile.Microphone 14 captures the displacements due to vibration of plate on anacoustical track and transmits a corresponding signal to spectrumanalyzer 16. Using Fourier transformation, for example, processing thesignal furnishes the spectral density of power as a function of thefrequency, and the particular modes of plate vibration are representedvisually by the peaks of spectral density of power at frequenciescorresponding to these modes. The amplitude of these peaks is measuredin Pa²/Hz and any variation in amplitude signifies a modification in thecondition of the surface being analyzed. In this case also, anothertransformation can be used, such as time-frequency or waves, for signalprocessing.

To illustrate this method, FIG. 4 illustrates a sweater 18 beforescraping and FIG. 5 shows the same sweater 18 after passage through thescraping device. This machine is equipped with metallic claws belowwhich sweater 18 passes and which lift numerous fibers emerging from thesweater, forming a napped surface 19. Thus, the scraped sweater is verysoft to touch.

With reference to FIG. 6, when blade 13 rubs against unscraped sweater18, spectrum analyzer 16 furnishes curve C, with a spectral density ofpower as a function of frequency which has an amplitude peak of lessthan 1.00E-05 Pa²/Hz.

When blade 13 rubs against scraped sweater 18, this abundant pilesurface 19 provokes greater mechanical excitation and greatly amplifiesthe reaction of blade 13. The result is curve D with a spectral densityof power as a function of frequency which has, at the same frequency, anamplitude peak equal to 2.50E-05 Pa²/Hz.

This significant variation in amplitude between the peaks is indicativeof a modification in the condition of the analyzed surface, in thiscase, increased softness to touch.

With reference to FIG. 3, evaluation device 20 of the invention is aportable apparatus used to measure the condition of a surface 25, eitherfixed or moving relative to device 20. Evaluation device 20 comprises asupport 22 housing one end of a vibrating element consisting of arectangular blade 23 made of very thin steel. In this variation themeans for measuring the particular modes of vibration is apiezo-electric gauge 24 attached to blade 23 and associated with aspectrum analyzer 26, which is itself connected to an interface 27.

Spectrum analyzer 26 is selected for the same purpose as spectrumanalyzers 6 and 16, that is to transform the signal emitted by thepiezo-electric or piezo-resistive gauge 24 into spectral density ofpower as a function of frequency, with the result being visible oninterface 27.

Here again it is possible to provide in evaluation device 20 a secondprocessing device to transfer the data obtained from the angle of thespectrum into a value determined relative a predefined scale as afunction of the vibrating element or of the means of measuring theparticular modes of vibration, and according to the condition of theentire analyzed surface.

Evaluation device 20 also comprises a housing 21 enclosing support 22, ablade 23, a gauge 24, a spectrum analyzer 26 and an interface 27,forming a compact device. Housing 21 comprises in its base an opening 28for the passage of the free extremity of blade 23. It also is equippedwith wheels 29 so evaluation device 20 can be easily displaced on thesurface to be analyzed 25.

Evaluation device 20 is used according to the following procedure: theoperator moves housing 21 along the surface 25 to be analyzed in thedirection indicated by arrow E. Support 22 is attached in housing 21 ata height allowing the free extremity of the blade 23, which extendsthrough opening 28, to rub against the surface 25 to be analyzed whileblade 23 bends slightly. Because of the interaction between the plateand the textile, the plate begins to vibrate in its particular mode.Piezo-electric gauge 24 measures variations in constraint relative tothe dynamic vibrating state of blade 23 and transmits a correspondingsignal to spectrum analyzer 26. Using a Fourier transformation, forexample, to process the signal, furnishes the spectral density of poweras a function of frequency and a visual display of the particular modesof vibration by the plate as peaks of spectral power density at thefrequencies corresponding to these modes. The amplitude of these peaksis measured in V²/Hz and any variation in amplitude signifies amodification of the condition of the analyzed surface. Moreover, othertransformations such as time-frequency or wave transformation may beused to process the signal.

With reference to FIG. 7, evaluation device 30 according to theinvention, which may be portable, takes the form of a housing (notshown) and is used to measure the surface condition of a sample 35 whichis either fixed or moving relative to device 30. Evaluation device 30comprises a support 32 housing one extremity of a vibrating elementconsisting of a rectangular blade 33 made of very thin steel. Support 32may take the form of a cylindrical bar. Said support 32 movesrotationally and may rotate continuously, as shown by arrow 34, oralternately, as shown by arrow 31. In this variation the means formeasuring vibrations is a piezo-electric or piezo-resistive gauge 36attached to blade 33 and associated with a spectrum analyzer (not shown)which is itself connected to an interface (not shown).

Thus, the evaluation device according to the invention and its methodprovide an analysis of the particular modes of vibration by a vibratingelement moving in relation to a surface for analysis, regardless of itsshape and material, and produces by this indirect measurement anassessment of the condition of various surfaces, regardless of theirstructure (periodic or not), their composition, or how they areobtained. These features cannot be obtained using current measurementmethods, which directly analyze the reaction of the surface to someforce, for example mechanical, optical, or electromagnetic force.

The present invention may be used in all endeavors where it is necessaryto assess surface condition and especially, to evaluate its softness totouch, such as the textile and cosmetics fields, the automotiveindustry, the detergent and household products industry, and inmanufacturing various objects. It can also be used to evaluate softnessto touch of living systems such as skin or hair as a result of applyingcosmetic products, since the evaluation device is capable of operatingin vivo.

In particular, several vibrating elements may be provided in a singleevaluation device. The vibrating element or elements may take numerousdifferent forms. First, it may have a shape with two dimensions that areinconsequential relative to a third: a stem that may or may not berigid, flat or curved, of any section, any shape, hollow, grooved, orsolid. There may also be an assemblage of several rods supported in amanner known in the art.

The shape of the vibrating element may have one dimension that isinconsequential relative to the two others, for example, a blade or aflat beam that may or may not be rigid, flat, or curved, of any sectionor any shape, hollow, grooved, or solid, or an assemblage of several ofthese vibrating elements.

Finally, the shape of the vibrating element may have no inconsequentialdimensions. In this case it may be any size, closed or not closed, rigidor not, flat or curved, of any section or any shape, hollow, grooved, orsolid, or any assemblage of several of these shapes.

The shape of the vibrating element may be an assemblage of differentshapes each having either one, two, or no dimensions that areinconsequential relative to the others.

The vibrating element may be made of materials other than thosedescribed above, namely a metal, organic, or mineral material ofnatural, artificial, or synthetic origin, or even a composition ofseveral of these materials.

The vibrating element may be attached on a slant with one of thefollowing mechanical connections: unidirectional or bidirectional pivot,sliding pivot, spherical pivot with or without a finger, linear,sliding, plane abutment, or point, allowing it between 0 and 5 degreesof movement.

The means for measuring the particular modes of vibration by thevibrating element may consist of sensors which measure:

kinematic values such as displacement, speed, acceleration;

dynamic values connected with the vibrating element such as force ormoment, or associated with the material such as constraint, deformation,or deformation speed;

environmental values such as acoustics, thermal conditions, andradioactivity.

The sensor or sensors used are founded on the following technologies:mechanical, acoustical, electrical, electrostatical, electromagnetic,electronic, optical, optoelectronic, chemical, thermal, radioactive. Itis also possible to use a viscous, liquid, or gaseous fluid as themedia. A combination of these technologies is also possible.

For signal processing, it is possible to use any mathematics or physicsmethod for analyzing an analog, discrete, quantified or digital signal.

The present invention is not limited to the exemplary embodimentsdescribed, but extends to any modification and variation obvious to oneskilled in the art while remaining with the scope of protection definedin the attached claims.

What is claimed is:
 1. An evaluation device (1, 10, 20, 30) forevaluating a surface condition of a material (5, 15, 25, 35); theevaluation device comprising: a support (2, 12, 22, 32) having avibration element (3, 13, 23, 33) attached thereto; wherein thevibration element (3, 13, 23, 33) is bendable and a remote free end ofthe vibration element (3, 13, 23, 33) sufficiently contacting thesurface of the material (5, 15, 25, 35) so as to arch the vibrationelement (3, 13, 23, 33), the vibration element (3, 13, 23, 33) beingmoved relative to the surface of the material (5, 15, 25, 35) to causethe at least one vibration element (3, 13, 23, 33) to vibrate; amechanism (4, 14, 24) carried by the vibration element (3, 13, 23, 33)for measuring particular modes of vibration of the vibration element (3,13, 23, 22) and furnishing a signal corresponding to the particularmodes of vibration; a device (6, 16, 26) for processing and analyzingthe furnished signal corresponding to the particular modes of vibrationand producing data, corresponding to the furnished signal, indicative ofthe surface condition of the material (5, 15, 25, 35); an interface (7,17, 27) for displaying the data; and a second processing device (6′) fortransforming the data indicative of the surface condition of thematerial (5, 15, 25, 35) into a value quantifying softness of thesurface condition of the material (5, 15, 25, 35).
 2. The evaluationdevice according to claim 1, wherein the material (5, 15, 25, 35) isselected from the group comprising at least the following: a metallicmaterial, an organic material, a natural mineral material, an artificialmineral material, a mineral material of synthetic origin, andcompositions of at least two of these materials.
 3. The evaluationdevice according to claim 1, wherein the vibration element (3, 13, 23,33) is made of material selected from the group comprising at least thefollowing: a metallic material, an organic material, a natural mineralmaterial, an artificial mineral material, a mineral material ofsynthetic origin, and compositions of at least two of these materials.4. The evaluation device according to claim 1, wherein the mechanism (4,24, 34) for measuring particular modes of vibration of the vibrationelement (3, 23, 33) is a sensor which measures at least one physicalvalue associated with the vibration element (3, 23, 33).
 5. Theevaluation device according to claim 30, wherein the mechanism (14) formeasuring particular vibration modes by the vibrating element (13) is asensor which measures at least one value associated with a correspondingenvironment.
 6. The evaluation device according to claim 1, wherein themechanism (4, 14, 24) for measuring particular modes of vibration of thevibration element (3, 13, 23, 33) employs technology selected from thegroup comprising: mechanical technology, acoustical technology,electrical technology, electrostatical technology, electromagnetictechnology, electronics technology, optical technology, optoelectronictechnology, chemical technology, thermal technology, radioactivetechnology, and a combination of at least two of these technologies. 7.The evaluation device according to claim 1, wherein the signalprocessing and analyzing device (6, 16, 26) effects an analysis of thesignal using a method selected from the group comprising at least amathematics method and physics methods.
 8. The evaluation deviceaccording to claim 1, wherein the signal processing and analyzing device(6, 16, 26) effects an analysis of the signal using a physics methods,and the physics method effects a transformation of the signal selectedfrom the group consisting of at least Fourier transformation, atime-frequency transformation, and a wave transformation.
 9. Theevaluation device according to claim 1, wherein the vibration element(3, 13, 23, 33) is attached, via a mechanical connection, to the support(2, 12, 22, 32) at an angle, and the mechanical connection is selectedfrom the group comprising: unidirectional pivot, a bidirectional pivot,a sliding pivot, a spherical pivot with a finger, a spherical pivotwithout a finger, a linear connection, a sliding connection, a planarabutment connection, and a point abutment connection allowing between 0and 5 degrees of movement.
 10. The evaluation device according to claim1, wherein the evaluation device comprises a housing (21) which protectsthe vibrating element (23) and the support (22), and the housing (21)comprises at least one opening (28) therein which allows passage of aportion of the vibrating element (23) therethrough.
 11. The evaluationdevice according to claim 10, wherein the mechanism (24) for measuringthe particular vibration modes, the processing and analysis device (26),and the interface (27) are at least partially located within the housing(21).
 12. A method of using an evaluation device (1, 10, 20, 30) forevaluating a surface condition of a material (5, 15, 25, 35); theevaluation device comprising: a support (2, 12, 22, 32) having avibration element (3, 13, 23, 33) attached thereto; wherein thevibration element (3, 13, 23, 33) is bendable and a remote free end ofthe vibration element (3, 13, 23, 33) sufficiently contacting thesurface of the material (5, 15, 25, 35) so as to arch the vibrationelement (3, 13, 23, 33), the vibration element (3, 13, 23, 33) beingmoved relative to the surface of the material (5, 15, 25, 35) to causethe at least one vibration element (3, 13, 23, 33) to vibrate; amechanism (4, 14, 24) carried by the vibration element (3, 13, 23, 33)for measuring particular modes of vibration of the vibration element (3,13, 23, 22) and furnishing a signal corresponding to the particularmodes of vibration; a device (6, 16, 26) for processing and analyzingthe furnished signal corresponding to the particular modes of vibrationand producing data, corresponding to the furnished signal, indicative ofthe surface condition of the material (5, 15, 25, 35); and an interface(7, 17, 27) for displaying the data; the method comprising the steps of:inducing relative motion between the evaluation device (1, 10, 20, 30)and the material (5, 15, 25, 35) to cause the vibration element (3, 13,23, 33) to vibrate; measuring at least one particular mode of vibrationof the vibrating element using the mechanism (4, 14, 24) for measuringparticular modes of vibration; processing and analyzing the furnishedsignal, using the processing and analysis device (6, 16, 26), to obtaindata, corresponding to the furnished signal, indicative of the surfacecondition of the material (5, 15, 25, 35); and transforming the dataindicative of the surface condition of the material (5, 15, 25, 35) intoat least one value quantifying the softness of the material (5, 15, 25,35).
 13. An evaluation device (1, 10, 20, 30) for evaluating a surfacecondition of a material (5, 15, 25, 35); the evaluation devicecomprising: a support (2, 12, 22, 32) having a vibration element (3, 13,23, 33) attached thereto; wherein the vibration element (3, 13, 23, 33)is elastic and the elastic vibration element (3, 13, 23, 33) engagingwith the surface of the material (5, 15, 25, 35); the vibration element(3, 13, 23, 33) being moved relative to the surface of the material (5,15, 25, 35) to cause solely the at least one vibration element (3, 13,23, 33) to vibrate; a mechanism (4, 14, 24) for measuring particularmodes of vibration of the vibration element (3, 13, 23, 22) andfurnishing a signal corresponding to the particular modes of vibration;a device (6, 16, 26) for processing and analyzing the furnished signalcorresponding to the particular modes of vibration and producing data,corresponding to the furnished signal, indicative of the surfacecondition of the material (5, 15, 25, 35); an interface (7, 17, 27) fordisplaying the data.